pigmented system is the dispersion of pigment. Successful The intensity of a beam of light on passing through a dilute dispersion is imperative if optimum optical properties are to pigment dispersion is attenuated as a result of absorption and be obtained. Determining the degree of pigment dispersion scattering of light by the pigment particles. It was found that the is of fundamental importance, because it affects the optical particle size distribution of an organic pigment not only controls properties of a pigmented system. There are various methods the light scattering but also affects the light absorption. As the for the determination of the dispersion degree of organic milling time increases, the absorption coefficient increases while pigments, including sedimentation (6), electron microscopy the scattering coefficient decreases. The peak-to-valley ratio ob- , and colorimetry (8) techniques, but their high demands tained from the extinction spectra of the pigment dispersions can on sample preparation or expensive instrumentation more or be used to determine the dispersion degree of organic pigments, and this method was confirmed by particle size measurements. less limit their application. It is well known that organic α§ 1998 Academic Press pigments are relatively difficult to disperse, especially in Key Words: pigment dispersion; dispersion degree; absorption; aqueous systems. Thus, any technique that would help to scattering.
describe the state of dispersion in such systems could be of great value, particularly if it could also be used as a quality control tool.